This may not be relevant to your particular problem (the problem sounds slightly different), but just in case, here is a copy of something I posted recently for someone else on this forum who was having System restore problems:
If you have Norton Internet Security 2006 or 2007 installed on a Windows XP machine it could be that you have "product protection" switched on in the Norton configuration. This means your computer will still create restore points, but you won't be able to restore to any of those created after Norton was installed. The following link tells you how to get around this, but it won't make your "dodgy" restore points usable.
http://bertk.mvps.org/html/symantecdoc1.html
I had this problem and as soon as I followed these instructions, no problem!
(Edited to apologise for serious over-use of the word "problem" !!)
